Sea+Floor+Spreading

Earlier theories (e.g., by [|Alfred Wegener] and [|Alexander du Toit]) of continental drift were that [|continents] "plowed" through the sea. The idea that the seafloor itself moves (and carries the continents with it) as it expands from a central axis was proposed by[|Harry Hess] from [|Princeton University] in the 1960s[|[1]]. The theory is well-accepted now, and the phenomenon is known to be caused by [|convection] currents in the plastic, very weak upper mantle, or [|asthenosphere]. http://en.wikipedia.org/wiki/Seafloor_spreading
 * [|Seafloor] spreading** occurs at [|mid-ocean ridges], where new [|oceanic crust] is formed through [|volcanic activity] and then gradually moves away from the ridge. Seafloor spreading helps explain [|continental drift] in the theory of [|plate tectonics].